1. Field of the Invention
The present invention relates generally to the field of sensors for determining the position of an object and, more particularly, to an apparatus which uses magnetic sensors in cooperation with two magnetic components which can be combined as a single element or employed as separate elements that are attached to the object whose position is being sensed, wherein one of the magnetic components provides a reference signal that is used to correct for changes in condition which do not directly relate to movement of the object being sensed.
2. Description of the Prior Art
Many techniques for determining the position of an object are available to those skilled in the art. For example, simple systems can utilize limit switches to determine when a moving object reaches a particular predetermined position in space. To define the position of a moving object with more specificity, LVDT's or RVDT's can be used.
U.S. Pat. No. 4,707,695, which issued to Takahashi et al. on Nov. 17, 1987, discloses a magnetic position sensor that provides a detector for receiving a reference position signal in movement from an encoder track and a reference track arranged on a member included in a magnetic position sensor. It also comprises magnetic pick ups respectively confronting to the encoder track and the reference track. Both tracks jointly yield a position reference signal.
Those skilled in the art are also familiar with resolvers or rotation counters which can be used in situations where rotatable shafts are associated with the movement of an object to be monitored. Depending on the particular application, each type of position determining system provides certain advantages or disadvantages. For example, a particular application may require the position monitoring system to undergo severe changes in temperature or pressure. Other circumstances may require a minimum of moving parts because of exposure to adverse elements which would be captured between moving parts.